Microstructure and gene expression influence gyrification in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis is a fatal neurodegenerative disease involving progressive degeneration of upper and lower motor neurons. Beyond well-established grey and white matter pathology, alterations in cortical gyrification have recently been observed, yet their clinical relevance and molecular underpinnings remain to be understood. Here, we investigated this premise by examining its microstructural and transcriptional basis in 60 patients with amyotrophic lateral sclerosis (median age = 55, range = 25-72 years) and 60 matched controls (median age = 56, range = 27-72 years) using structural and diffusion MRI. Patients exhibited a significant reduction in local gyrification index within bilateral precentral and postcentral gyri, left middle frontal gyrus and left superior parietal lobule. This was accompanied by reduced fractional anisotropy in the white matter tracts, primarily involving the corticospinal tract and corpus callosum. Higher local gyrification index and fractional anisotropy values were associated with better motor function as measured by the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised, and local gyrification index also showed positive associations with global cognitive status. A mediation analysis indicated that fractional anisotropy partially accounted for the relationship between local gyrification index and functional disability, suggesting that disrupted white matter pathways contribute to the clinical impact of gyrification changes. To explore underlying mechanisms, we integrated neuroimaging findings with transcriptomic data from the Allen Human Brain Atlas. Regions of reduced local gyrification index showed spatial convergence with cortical expression of amyotrophic lateral sclerosis-related genes such as <i>TARDBP</i> and <i>C9orf72</i>, enriched for biological processes related to protein aggregation, axon guidance and synaptic signalling. Together, these findings suggest that cortical gyrification abnormalities in amyotrophic lateral sclerosis are closely linked to white matter degeneration, functional impairment and genetic vulnerability, thereby offering an integrative window into the multiscale pathology of amyotrophic lateral sclerosis.